[PATCH] Remaining sparse warnings in allnoconfig

Attached is a smallish patch for couple trivial sparse warnings in
allnoconfig build and more importantly an "excuses" text file explaining
why the rest have not been fixed.

Basically all of them (with the exception of the one in Andrews tree) need
some serious re-engineering.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/dcookies.h

@@ -50,7 +50,7 @@ int get_dcookie(struct dentry * dentry, struct vfsmount * vfsmnt,
 
 struct dcookie_user * dcookie_register(void)
 {
-	return 0;
+	return NULL;
 }
 
 void dcookie_unregister(struct dcookie_user * user)

include/linux/pm.h

@@ -159,7 +159,7 @@ static inline struct pm_dev *pm_register(pm_dev_t type,
 					 unsigned long id,
 					 pm_callback callback)
 {
-	return 0;
+	return NULL;
 }
 
 static inline void pm_unregister(struct pm_dev *dev) {}

init/initramfs.c

@@ -169,7 +169,7 @@ static int __init do_collect(void)
 	memcpy(collect, victim, n);
 	eat(n);
 	collect += n;
-	if (remains -= n)
+	if ((remains -= n) != 0)
 		return 1;
 	state = next_state;
 	return 0;

kernel/sysctl.c

@@ -2162,7 +2162,7 @@ int proc_doulongvec_ms_jiffies_minmax(ctl_table *table, int write,
 struct ctl_table_header * register_sysctl_table(ctl_table * table, 
 						int insert_at_head)
 {
-	return 0;
+	return NULL;
 }
 
 void unregister_sysctl_table(struct ctl_table_header * table)